The current state of the art substantially envisages two different types of packaging systems for items in bundles.
A first technique envisages the use of heat-shrink film that is wrapped around the items to be packaged and then shrinks adhering around them by being passed into a relevant oven.
A second technique envisages the use of a cold processing shrink-wrapping machine wherein a reel of extensible film rotates around a group of items held by relevant means for holding them, such as for example in WO 2011/024050. The advantage of such a solution is that the use of an oven for heat-shrinking the film is avoided, as well as less film being used. The only slight drawback of the use of cold extensible film, instead of heat-shrink film, consists of the impossibility to print on such film since the printing would become deformed in the step of extending the film to make it adhere to the items to be packaged.
Cold processing shrink-wrapping machines are however rather complex since the reel of extensible film (which is rather large) is made to rotate around the items to be packed, while they are kept still by relevant means for holding them. This implies the need for sufficient space to make the reel rotate numerous times around the items, as well as the need for special means, sufficiently strong considering the weight of the reel, particularly when it is almost full, which envisage making the reel rotate around the items at such a speed as to allow packaging in a short time. DE 10 2011 081704 A1 shows a packaging machine in which the items are held laterally and the film is wrapped around them through rotations about a vertical axis. In the event in which the items are containers or bottles fed in an erect position, such a machine produces a bundle in which the film is laterally wrapped around the containers leaving the bottom and the mouth of the containers uncovered (i.e. not wrapped or protected), which are hence subject to getting dirty, lacking the necessary hygiene conditions, particularly for containers intended for food.
The same drawbacks are also shown in DE 3902919 A1.